On-site Linux support costs more and that is a factor that needs to be taken into account.

Based on what evidence? you throw that out there and provide nothing to back it up nor do you even take into account one can use Zenworks for large deployments thus just as simple as managing a network of Windows servers and desktops.

Switching to Linux doesn't come with a lock-in? What about dependence on Oracle for OpenOffice? There is also a lock-in to a smaller business software library.

I think a case can be made for installing OO on XP boxes instead of upgrading an older version of Office but completely switching to Linux is likely to incur costs rather than savings.

So stick with Windows XP and find yourself high and dry in a few years after support stops - excuse me but that sounds like the most stupid f-cking idea I've ever come across. While you're on the train of thought why don't you deploy Windows 2000 for sh-ts and giigles!

As for your first paragraph, how are you dependent on Oracle? OpenOffice.org is an open source project that has Red Hat, Novell, Oracle and numerous individual contributors; there is nothing stopping the government, as they do for other projects, to setup a dedicated group of half a dozen programmers to address problems with OpenOffice.org for the whole public service. There is no 'vendor lock in' and as for 'smaller business software library' - you do know we're talking about enterprise customers not Bobby Jane's Toast Shop and her desire to have 100s of pointless widgets and applications. Are there few vendors? sure, but they're the vendors that actually count - who cares if there are 100 vendors on offer if only 10 of them are actually worth considering.